1. Field of the Invention
The present invention relates to the field of synthetic fibers, and in particular, the coating of ceramic fibers and woven articles comprised of ceramic fibers.
2. Description of the Related Art
Ceramic materials are attractive for a wide range of applications, offering important advantages over other materials. Such advantages include, for example, low weight, high-temperature resistance and thermal stability, erosion resistance, chemical inertness and environmental stability. Ceramic materials are therefore highly desirable for a number of applications despite their brittleness, flaw sensitivity and propensity for catastrophic failure. It is highly desirable to utilize the advantages of ceramic materials while increasing both the strength and toughness of ceramic materials thereby overcoming the drawback of their brittle properties.
A common technique to reduce the brittle behavior of ceramics involves the creation of ceramic matrix composites by incorporating high-strength ceramic fibers as reinforcements into ceramic matrices. Numerous commercially available fibers are available for reinforcing-ceramic matrices (e.g., Nextel 610 and Nextel 720, manufactured by the 3M Company, and Sylramic, manufactured by Composite Optics, Inc.). In order to realize the benefits of ceramic fiber reinforcement, the matrix must transfer loads to the fibers but become decoupled from the fibers during fracture so that the fibers remain intact and thus continue to bear the loads.
The load transfer and decoupling capabilities of the composite can be greatly enhanced through the use of functional fiber coatings (such as carbon, boron carbide, hibonite and monazite, for example). Various methods have been used to apply such coatings to ceramic fibers, including chemical vapor deposition (CVD) and continuous dip-coating using solution and sol derived precursors. These coating processes, which are time and labor intensive, are generally applicable to multi-filament tows and are not typically amenable to coating cloths or woven preforms of ceramic fibers. Existing methods for coating woven cloths and preforms, such as CVD, for example, are typically very costly, requiring considerable capital investments in the necessary equipment. In addition, such methods generally necessitate the handling of hazardous chemicals, which further imposes costs and complexities.
Accordingly, there is a need for an improved method of coating ceramic fibers and cloths and woven preforms of ceramic fibers.